Method of conditioning ink form rolls



United States Patent 3,257,945 METHOD OF CONDITIONING INK FORM ROLLSWilliam F. Smith, Jr., 504 S. Lake Shore Drive, Mundelein, Ill. NoDrawing. Filed Nov. 13, 1962, Ser. No. 237,356 2 Claims. (Cl. 101426).This invention relates generally to innovations and improvements in theart of printing and to novel compositions for bringing about suchimprovements. More specifically, this invention applies to methods ofprinting where ink or coating material is applied to a printing plate bymeans of an ink carrying roll. As used herein, the term printing refersnot only to wording, figures and pictures, but also to backgrounddesigns and solid printed or coated areas. The printing may be black orin various colors, including multi-color printing.

It is common in printing to transfer ink from a fountain or reservoirthrough a series of rubber, metal, and/or plastic rolls to the surfaceof the printing plate. Various known types of printing plates areattached to the plate cylinder such as metal, rubber, plastic or paper.From the printing plate the ink or coating material is either directlyapplied to the surface to be printed or applied to an intermediate.cylinder which'in turn applies the ink or coating material to thesurface to be printed. The last in the series of rolls that bring theink to the printing plate are normally called form rolls. These formrolls actually contact the surface of the printing plate. These ink formrolls are used in conventional presses whether the type of printing betypographic (e.g. letter press) or planographic (e.g. offset orlithographic).

One problem that has plagued operators of printing presses has been thatof foreign matter sticking to the surface of the printing plate so as toprevent ink from being applied to the printed sheet in that area. Suchforeign matter is commonly referred to by the press operators ashickies.

These hickies necessitate:

(a) Shutting the press down and cleaning the foreign matter from thesurface of the plate.

(b) Continuing to run the press and sorting and discarding bad sheetsaway when the job is completed.

(0) Operators risking permanent physical injury by attempting to removethe foreign matter from the printing plate with their fingernails whilethe press is in operation.

I have discovered, in accordance with my present invention that if atacky material having the tacky properties of, or closely similar tothose of, urethane rubber prepolymer or monomer is applied to thesurface of at least one roll in the roller chain, preferably one of theso-calied ink form rolls, that the formation of hickies on the printingplate can be greatly minimized, and usually entirely prevented. After aperiod of running, e.g. five to eight hours, it will usually benecessary to clean off the ink rolls and re-apply the tacky materialthereto. However, as long as the tacky deposit is maintained, hickiescan be avoided.

Accordingly, the object of the invention, generally stated, is a methodof, and compositions for, eliminating poor quality printed sheets due toforeign matter or hickies that stick to a printing plate or surface.

A more specific object is the improvement inprinting I which comprisesmaintaining on at least one ink roll a deposit of a tacky substancehaving the tackiness properties of, or closely similar to those of,urethane rubber prepolymer and cleaning the rolls and re-applying thetacky substance as required.

Another important object of the invention is the provision ofcompositions for imparting such a tacky deposit on the surface of aprinting press ink form roll comprising urethane rubber prepolymerdissolved in a volatile carrier such as methylene chloride.

A further object of the invention is a pressure package, or aer-osolpackage, containing a volatile propellant and a composition forimparting a tacky deposit on the surfaces of printing press form rollscomprising urethane rubber prepolymer dissolved in methylene chloride.

Certain other objects of the invention will, in part, be obvious andwill in part appear hereinafter.

I have discovered that a preferred material for giving the correcttackiness to the ink form rolls of the printing press is urethane rubberprepolymer or monomer. This is a known material that is available fromseveral commercial sources such as Thiokol Chemical Corp. (Solithane 113and291), and E. I. du Pont de Nemou'rs and Co. (Adiprene L100, L167,L315). Such materials are liquids and have isocyanate'contents rangingfrom about 3% to about 4.3% by weight.

While the urethane rubber prepolymer is the substance of choice, othermaterials that will afford similar tacky surfaces may be used such asthe chlorinated biphenols such as commercially available from MonsantoChemical Co., under the trade name of Aroclor, or the polybutenesmanufactured by the Oronite Co., or other slow drying tacky substancesof a similar nature.

The urethane prepolymers and these other substances may be classified astacky, non-drying substances that may be solventized in a volatilesolvent such as methylene chloride.

The composition may be applied to the ink form rolls of a printing pressin several ways such as by wiping on, brushing on, spraying on, ordipping the rolls in the solution. Spraying on from a-pressure packageof aerosol can or container constitutes a preferred technique ofapplication in that a uniform thin deposit of the urethane or othertacky substance may readily be obtained Without removing the ink formrolls from the press.

A preferred composition for either method of application is 1 part byweight of urethane'rubber prepolymer dissolved in 10 parts by weight ofmethylene chloride. Other volatile solvents that may be used includemethyl ethyl ketone, toluol, acetone or butylacetate.

It appears that the tacky deposit of urethene rubber has just theappropriate tackiness to keep the printing plate clean and free ofhickie forming foreign substances without interferring with the normaloperation of the printing plate. After some time in operation, e.g. fiveto eight hours, it will be advisable to stop the press and to clean theink form rolls so as to removethe tacky deposit therefrom which by thistime will begin to lose its'efficiency. A new deposit may be readilyformed and the operation of the press resumed. Any suitable solvent maybe used for removing or cleaning the ink form rolls such as themethylene chloride solvent itself. Thus, the frequency of shut down forpreventing hickies (not to mention the safety factor) is greatly reducedand the saving in time and labor and increase in production are such asto exceed by many times the cost of the compositions.

- What I claim as new is:

1. In printing the improvement which comprises applying to the surfaceof at least one ink form roll of the press, liquid urethane rubberprepolymer having an isocyanate content in the range of from about 3% toabout 4.3% by weight, and periodically cleaning said form roll andapplying an additional amount of said urethane rubber prepolymer.

2. The improvement of claim 1 wherein said urethane rubber prepolymer isapplied as an aerosol spray.

(References on following page) 3 4 v 5 References Cited by the ExaminerHerzka: Pressurized Packaging; Butterworth & Co.;

1958, pp. 311, 325. v 5 UNITED STATES PATENTS Du Pont: Adiprene L., ALiquid Urethane Elastomer; 2,243,43 5 1941 ormond 1 1*211 DevelopmentProducts Report No. 10; E. I. du Pont de 2,653,540 9/1953 Johnson101-426 5 Nemours nd 30., 1958- 2,975,157 3/1961 Katz. 3 105 0 2 9 19 3Graham et ALEXANDER H. BRODMERKEL, Primm y Examiner;

MORRIS LIEBMAN, Examiner.

OTHER REFER S ENCE L. T. JACOBS, Assistant Examiner.

Inland Printer, The; May 1938; page 77. 10

1. IN PRINTING THE IMPROVEMENT WHICH COMPRISES AP PLYING TO THE SURFACEOF AT LEAST ONE INK FORM ROLL OF THE PRESS, LIQUID URETHANE RUBBERPREPOLYMER HAVING AN ISOCYANATE CONTENT IN THE RANGE OF FROM ABOUT 3% TOABOUT 4.3% BY WEIGHT, AND PERIODICALLY CLEANING SAID FORM ROLL ANDAPPLYING AN ADDITIONAL AMOUNT OF SAID URETHANE RUBBER PREPOLYMER.